Various optical methods may be applied to measurement and/or modeling of an object. Photogrammetry is a technique that extracts measurements from photographs of an object. For example, photogrammetry may be used to produce maps (e.g., aerial photogrammetry) and/or to produce models of industrial installations (close-range photogrammetry) from photographs. In photogrammetry, images of a scene are captured from different angles and two-dimensional measurements of objects are converted into three-dimensional coordinates via bundle adjustment mathematical routines. Photogrammetry requires the use of targets to correlate the images and is limited to the measurement of visual indicators such as points and natural features (i.e. corners, edges, cylinders). Close-range Photogrammetry can provide good results when multiple images from different angles that produce good intersection geometry and high redundancy are provided. Stereoscopic photogrammetry allows the measurement of points on surfaces but has limitations in terms of accuracy because the stereoscopic sensor has only two lines of sight that are quasi-parallel.
Laser Triangulation is an optical technique that may be used for high density measurement of small surfaces. In laser triangulation, a laser source that projects, for example, a line, dot, or pattern, is mounted with an optical sensor (e.g., a camera) in accordance with a predetermined calibrated geometry. The laser projection is triangulated by the optical sensor. To provide multiple measurements, a rotating mirror may be mounted in front of the laser, allowing the optical sensor to “scan” a large surface with a high density of points.